Certain stem cells and T cells originate in bone marrow and circulated in the blood. One option for treating cancers of the blood and bone marrow is to kill existing cells, e.g., through radiation or chemotherapy, and transplant similar cells from a healthy donor, referred to as an allogeneic hematopoietic stem cell transplant (allo-HSCT). A major complication of allo-HSCT is graft versus host disease (GVHD). Thus, there is a need to identify improved methods of preventing GVHD.